Shower plate sintered integrally with gas release hole member and method for manufacturing the same

ABSTRACT

A shower plate is disposed in a processing chamber in a plasma processing apparatus, and plasma excitation gas is released into the processing chamber so as to generate plasma. A ceramic member having a plurality of gas release holes having a diameter of 20 μm to 70 μm, and/or a porous gas-communicating body having pores having a maximum diameter of not more than 75 μm communicating in the gas-communicating direction are sintered and bonded integrally with the inside of each of a plurality of vertical holes which act as release paths for the plasma excitation gas.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 12/446,913, filed on Jan. 25, 2010, which claims a priority to andthe benefit of Japanese Patent Application No. 2006-287934, filed onOct. 23, 2006, the disclosures of which are incorporated herein in itsentirety by reference.

TECHNICAL FIELD

The present invention relates to a plasma processing apparatus, and moreparticularly, to a shower plate used for a microwave plasma processingapparatus and a method of manufacturing the shower plate, a plasmaprocessing apparatus using the shower plate, a plasma processing method,and a method of manufacturing an electronic apparatus.

BACKGROUND ART

Plasma processing and plasma processing apparatuses have becomeindispensable in the manufacturing of ultra-fine semiconductor deviceswhich are called recently deep submicron devices or deep sub-quartermicron devices, having a gate length of 0.1 μm or less, or in themanufacturing of high resolution flat panel display devices includingliquid crystal display devices.

Various plasma exciting methods are conventionally used for plasmaprocessing apparatuses used to manufacture semiconductor devices orliquid crystal display devices. In particular, parallel-plate type highfrequency excitation plasma processing apparatuses or induction-coupledtype plasma processing apparatuses are generally used as plasmaprocessing apparatuses. However, these conventional plasma processingapparatuses have a drawback in that since the formation of plasma is notuniform and regions of high electron density are limited, it isdifficult for conventional plasma processing apparatuses to achieveuniform processing over the entire surface of a substrate to beprocessed at a high processing speed, that is, at a high throughput.This problem becomes particularly serious when a substrate having alarge diameter is processed. Further, these conventional plasmaprocessing apparatuses suffer from some inherent problems, such asdamage to the semiconductor devices formed on the substrate to beprocessed due to their high electron temperature, and, severe metalcontamination caused by sputtering of a processing chamber wall. Thus,it is becoming more difficult for conventional plasma processingapparatuses to satisfy the constant demand for further miniaturizationof semiconductor devices or liquid crystal display devices and furtherimprovement in productivity.

To solve this difficulty, a conventional microwave plasma processingapparatus that uses high-density plasma excited by a microwave electricfield without using a direct current magnetic field has been proposed.For example, a plasma processing apparatus, having a construction inwhich microwaves are radiated to a processing chamber from a planarantenna (radial-line slot antenna) having a number of slots arranged toradiate uniform microwaves, the gas inside the processing chamber isionized by the microwave electric field to generate plasma, has beenproposed (for example, refer to Japanese Laid-Open Patent PublicationNo. Hei 9-63793 (hereinafter, referred to as Reference 1)). In theplasma excited by the microwave electric field, it is possible torealize a high plasma density over a wide area below the planar antenna,and it is possible to conduct uniform plasma processing in a short time.Further, since the electron temperature is low in the plasma formed bythe microwave electric field, it is possible to avoid damage beingcaused to or metal contamination of the substrate to be processed.Further, since it is possible to excite uniform plasma over a large areaof a substrate, the above-mentioned technology can be easily applied tothe manufacturing process of semiconductor devices by usingsemiconductor substrates having large diameters or manufacturing oflarge liquid crystal display devices.

Plasma processing apparatuses use a shower plate including a pluralityof vertical holes as gas release holes in order to uniformly supply agas for exciting plasma into a processing chamber. However, when usingthe shower plate, plasma formed right below the shower plate may flowbackwards through the vertical holes of the shower plate, which causesan abnormal discharge or deposition of gases, and thus transmissionefficiency of microwaves for plasma excitation or yield of devicesdeteriorates.

Many structures of the shower plate have been suggested to prevent thereverse flow of plasma through the vertical holes.

For example, in Japanese Laid-Open Patent Publication No. 2005-33167(hereinafter, referred to as Reference 2), the hole diameter of a gasrelease hole formed in the leading end of a vertical hole of a showerplate is set to not greater than twice the sheath thickness of plasmaformed right below the shower plate. However, it is insufficient toreduce the hole diameter of the gas release hole in order to prevent thereverse flow of plasma. In particular, if a plasma density is increasedfrom 10¹² cm⁻³, which is a conventional value, to 10¹³ cm⁻³ in order toreduce damage and increase a processing speed, it is impossible toprevent the reverse flow of plasma by only controlling the hole diameterof the gas release hole since the reverse flow of plasma increases.Also, it is difficult to form the gas release hole having a micro holediameter by processing a hole of a shower plate body, and is problematicin terms of processability.

Japanese Laid-Open Patent Publication No. 2004-39972 (hereinafter,referred to as Reference 3) discloses the use of a shower plate that isa porous ceramic sintered body having gas permeability. The shower plateis for preventing the reverse flow of plasma by the walls of a pluralityof pores included in the porous ceramic sintered body.

However, the shower plate having general porous ceramic sintered bodysintered at a normal temperature and a pressure is not good in surfaceplanarization since the shower plate includes pores having a largedeviation between several μm and several tens of μm in terms of porediameters, has a large maximum crystal diameter of 20 μm, and does nothave a uniform structure. If a surface of the shower plate being exposedto plasma is the porous ceramic sintered body, an effective surface areaincreases, and electron and ion recombination of the plasma increases,which deteriorate power efficiency of excitation of plasma. In thisregard, the Reference 3 discloses, instead of wholly forming the showerplate as the porous ceramic sintered body, forming a structure of theshower plate formed of dense alumina in which an opening for releasinggas is formed, and the general porous ceramic sintered body sintered atthe normal temperature and pressure is fitted into the opening, and thengas is released through the porous ceramic sintered body. However, sincethe structure uses the porous ceramic sintered body sintered at theordinary temperature and pressure, the above-mentioned problem caused bypoor surface-planarization has not been solved.

Also, in International Publication WO06/112392 (hereinafter, referred toas Reference 4), the applicant of the present application has suggestedpreventing the reverse flow of plasma by not adjusting the structure ofa shower plate but adjusting a diameter size of a gas release hole. Inmore detail, the diameter size of the gas release hole is set less than0.1˜0.3 mm, and a tolerance accuracy of the diameter size is set towithin ±0.002 mm, and thus the reverse flow of plasma is prevented andno variation in the amount of released gas occurs.

However, when the shower plate has been actually used for a microwaveplasma processing apparatus under plasma density conditions of 10⁻³cm⁻³, as shown in FIG. 10, a discolored light brown portion is seen as aresult of the reverse flow of plasma into a space 402 for chargingplasma excitation gas formed between a shower plate body 400 and a coverplate 401 and a vertical hole 403 in communication with the space 402.

To address the above-mentioned problems, in Japanese Patent ApplicationNos. 2006-163357, 2006-198762, and 2006-198754 (hereinafter, referred toas References 5 through 7, respectively), the applicant of the presentapplication has suggested fitting a ceramic member having a plurality ofgas release holes or a porous gas-communicating body having porescommunicating in a gas-communicating direction into a vertical hole of ashower plate as a release path for plasma excitation gas.

In the References 5 through 7, the shower plate can prevent the reverseflow of plasma even under plasma density conditions of 10¹³ cm⁻³.

However, since the shower plate has been repeatedly used for a microwaveplasma processing apparatus, the ceramic member or the porousgas-communicating body fitted into the vertical hole of the shower platepartially or wholly comes out from the vertical hole of the showerplate. This is a result of a reduction in the adherence between theceramic body or the porous gas-communicating body and the vertical holeof the shower plate, caused by thermal stress or thermal deformationthat occurs when using the shower plate.

DISCLOSURE OF THE INVENTION Technical Solution

To solve the above and/or other problems disclosed in the References 5through 7, the present invention provides a shower plate for plasmareverse flow prevention purposes, comprising gas release hole members (aceramic member or a porous gas-communicating body) sintered and bondedintegrally without any space and disposed within vertical holes in theshower plate, so that the gas release hole members do not becomedetached from the vertical holes during use of the shower plate, andthus, there is no variation in the amount of gas released from eachvertical hole, the reverse flow of plasma can be more completelyprevented, and resulting in plasma excitation with high efficiency.

According to an aspect of the present invention, a ceramic member or aporous gas-communicating body is sintered and bonded with a verticalhole of a shower plate. A diameter of each of gas release holes of theceramic member may be between 20 μm to 70 μm, an aspect ratio of lengthsto hole diameters of the gas release holes of the ceramic member may beequal to or greater than 20, a maximum pore diameter of the porousgas-communicating body is equal to or less than 75 μm, and a porediameter of a narrow path along a gas-communicating path may be equal toor less than 10 μm, thereby more completely preventing the reverse flowof plasma.

In more detail, the shower plate disposed in a plasma processingapparatus and releasing plasma excitation gas into the plasma processingapparatus so as to generate plasma, wherein the ceramic member having aplurality of gas release holes having the diameter of 20 μm to 70 μmand/or the porous gas-communicating body having pores having the maximumdiameter of equal to or less than 75 μm, which communicate in agas-communicating direction, may be formed in the inside of each of aplurality of vertical holes as release paths for plasma excitation gas,and the ceramic member and/or the porous gas-communicating body may besintered and bonded integrally with the shower plate.

As described above, since the ceramic member or the porousgas-communicating body is sintered and integrally bonded without anyspace to be disposed within vertical holes in a shower plate as agas-communicating path, the ceramic member or the porousgas-communicating body is secured into the vertical holes of the showerplate, so that the ceramic member or the porous gas-communicating bodydoes not become detached from the vertical holes due to thermal stressor thermal deformation that occurs when using the shower plate, andthere is no variation in the amount of gas released from each verticalhole. Also, the Diameter of each of gas release holes of the ceramicmember is between 20 μm to 70 μm, the maximum pore diameter of theporous gas-communicating body is equal to or less than 75 μm, and thepore diameter of the narrow path along a gas-communicating path is equalto or less than 10 μm, thereby more completely preventing the reverseflow of plasma.

The ceramic member and the porous gas-communicating body used in thepresent invention may be formed of a low dielectric loss ceramicmaterial having a dielectric loss in the range of 5×10⁻³ and 1×10⁻⁵. Forexample, a high purity alumina ceramic material, a small amount of anparticle growth inhibition agent, an alumina ceramic material mixed withY₂O₃ and mullite, a material formed of Al₂O₃ and Y₂O₃, or a materialcontaining a garnet component that is a compound of Al₂O₃ and Y₂O₃, andfurther a ceramic material such as AlN, SiO₂, mullite, Si₃N₄, or SiAlON,can be used.

The aspect ratio of lengths to hole diameters of the gas release holesof the ceramic member may be equal to or greater than 20. FIG. 9 is aview for explaining the relationship between the aspect ratio of gasrelease holes and the reverse flow of plasma. If the pressure of aprocessing chamber of the plasma processing apparatus is reduced, themean free path increases, resulting in an increase of a distance ofelectrons forming plasma which linearly move forward. As such, ifelectrons linearly move forward, a plasma introducible angle θ shown inFIG. 9 is defined by the aspect ratio of the gas release holes A as itis. That is, if the aspect ratio of the gas release holes A increases,the plasma introducible angle θ is reduced, thereby preventing thereverse flow of the plasma. Since the aspect ratio of the gas releaseholes A is equal to or greater than 20, even if plasma density isincreased to 10¹³ cm⁻³, it is possible to dramatically stop the reverseflow of the plasma.

The gas-communicating path formed by the pores of the porousgas-communicating body having the maximum pore diameter equal to or lessthan 75 μm in communication may have the narrow path having the porediameter of equal to or less than 10 μm. Since the narrow path havingthe pore diameter is equal to or less than 10 μm, even if plasma densityis increased to 10¹³ cm⁻³, it is possible to dramatically stop thereverse flow of the plasma. In more detail, although the communicationof gas of the porous gas-communicating body is secured via thecommunicating pores, the gas-communicating path is bent in zigzag shape,and further has the narrow path equal to or less than 10 μm. In thisregard, since electrons or ions forming plasma tend to go straight, eventhough the plasma flows backwards to the porous gas-communicating body,most of the plasma collide with walls of the pores, and furthermore theplasma wholly collide in the narrow path having the pore diameter ofequal to or less than 10 μm, thereby preventing the reverse flow of theplasma.

As the ceramic member or the porous gas-communicating body is sinteredand integrally bonded within vertical holes in the shower plate asdescribed above, the shower plate may be manufactured by fitting theceramic member or the porous gas-communicating body into the verticalholes in the shower plate and then simultaneously sintering the showerplate and the ceramic member or the porous gas-communicating body fittedinto the vertical holes of the shower plate. To be more specific, withregard to the ceramic member and the porous gas-communicating body, inthe step of a powder molding body processed in a predetermined shape bymolding material powder of the ceramic member and the porousgas-communicating body, a debinded body of the powder molding body, apre-sintered body of the powder molding body, or a sintered body of thepowder molding body, and with regard to the shower plate, in the step ofa green body by molding material powder of the shower plate and byprocessing the vertical holes, a debinded body of the green body, apre-sintered body of the green body, or a sintered body of the greenbody, the ceramic member and the porous gas-communicating body arefitted into at least the leading ends of the vertical holes in theshower plate, and are then simultaneously sintered. In this case,molding conditions or debinding, pre-sintering, and sintering conditionsare adjusted in such a manner that the inner diameters of the verticalholes of the shower plate are almost the same as or slightly less thanthe outer diameters of elements fitted into the vertical holes after thesimultaneous sintering is performed. As such, the ceramic member and theporous gas-communicating body are fitted into the vertical holes of theshower plate before the shower plate is sintered, and then aresimultaneously sintered, thereby achieving a strong and secure fit ofthe ceramic member and the porous gas-communicating body into thevertical holes of the shower plate without any space.

Plasma excitation gas may be supplied to a plasma processing apparatusby using the shower plate of the present invention, plasma may begenerated by exciting the supplied plasma excitation gas by microwaves,and oxidizing, nitriding, oxynitriding, chemical vapor deposition (CVD),etching, or irradiating plasma may be performed with regard to asubstrate by using the plasma.

Effects of the Invention

According to the present invention, since a ceramic member or a porousgas-communicating body disposed within vertical holes in a shower plateis sintered and integrally bonded without any space for plasma reverseflow prevention purposes, there is no variation in the amount of gasreleased from each vertical hole and the ceramic member or the porousgas-communicating body does not become detached from the vertical holesduring use of the shower plate and the reverse flow of plasma can bemore completely prevented in the vertical holes which act as a releasepath for plasma excitation gas of the shower plate. An abnormaldischarge or deposition of gas in the shower plate can be prevented,thereby preventing deterioration of transmission efficiency ofmicrowaves for plasma excitation of deterioration of yield.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of a microwave plasma processingapparatus according to an embodiment of the present invention;

FIG. 2 is a schematic perspective view of horizontal holes and verticalholes of a shower plate shown in FIG. 1;

FIG. 3 is a detailed cross-sectional view of a vertical hole of theshower plate shown in FIG. 1;

FIG. 4 is views of another structure of the vertical hole of the showerplate shown in FIG. 1;

FIG. 5 is views of another structure of the vertical hole of the showerplate shown in FIG. 1;

FIG. 6 is a cross-sectional view of a microwave plasma processingapparatus according to another embodiment of the present invention;

FIG. 7 is a top plan view of the arrangement of horizontal holes andvertical holes of a shower plate shown in FIG. 6;

FIG. 8 is a schematic perspective view of the arrangement of the showerplate and a cover plate shown in FIG. 6;

FIG. 9 is a view for explaining the relationship between an aspect ratioof gas release holes and the reverse flow of plasma; and

FIG. 10 is a cross-sectional view of a conventional shower plate.

BEST MODE FOR CARRYING OUT THE INVENTION

The attached drawings for illustrating exemplary embodiments of thepresent invention are referred to in order to gain a sufficientunderstanding of the present invention, the merits thereof, and theobjectives accomplished by the implementation of the present invention.Hereinafter, the present invention will be described in detail byexplaining exemplary embodiments of the invention with reference to theattached drawings. Like reference numerals in the drawings denote likeelements.

Embodiment 1

FIG. 1 is a cross-sectional view of a microwave plasma processingapparatus according to an embodiment of the present invention. Referringto FIG. 1, the microwave plasma processing apparatus includes aprocessing chamber 102 from which gas is exhausted through a pluralityof gas exhaust ports 101. A holding stage 104 for holding a substrate103 to be processed is disposed in the processing chamber 102. In orderto uniformly exhaust gas from the processing chamber 102, a ring shapedspace is defined around the holding stage 104 of the processing chamber102. The plurality of gas exhaust ports 101 are arranged at equaldistances so as to communicate with each other in a ring shaped space,i.e., arranged in an axially symmetrical manner with respect to thesubstrate 103 to be processed. Gas from the processing chamber 102 canbe uniformly exhausted through the gas exhaust ports 101 according tothe arrangement of the gas exhaust ports 101.

A shower plate 106 is attached to an upper portion of the processingchamber 102 through a sealing O-ring 107 at a position corresponding tothe substrate 103 to be processed on the holding stage 104, as a part ofthe outer walls of the processing chamber 102. The shower plate 106 isformed of dielectric alumina having a diameter of 408 mm, a relativepermittivity of 9.8, and a low microwave dielectric loss (equal to orless than 1×10⁻⁴), and is in the form of a plate in which a plurality(230) of openings, i.e. vertical holes 105, are formed. Also, a coverplate 108 formed of alumina is attached to the processing chamber 102through a sealing O-ring 109 on an upper surface side of the showerplate 106, i.e., on an opposite side to the holding stage 104 withrespect to the shower plate 106.

FIG. 2 is a schematic perspective view of the arrangement of the showerplate 106 and the cover plate 108. Referring to FIGS. 1 and 2, aplurality of spaces 112 for charging plasma excitation gas supplied froma plasma excitation gas inlet port 110 through a gas supply hole 111which are open and communicate with the inside of the shower plate 106,are disposed between the upper surface of the shower plate 106 and thecover plate 108. In other words, grooves are formed in the lower surfaceof the cover plate 108 in the shower plate 106 side so that verticalholes 105 and a position corresponding to the gas supply hole 111communicate each other to form the spaces 112 between the shower plate106 and the cover plate 108. That is, the vertical holes 105 aredisposed to communicate with the spaces 112.

FIG. 3 is a detailed cross-sectional view of the vertical hole 105. Thelength of the vertical hole 105 is about 8˜21 mm, and the diameterthereof is equal to or less than 3 mm (preferably equal to or less than1 mm). A porous ceramic sintered body 114, which has a cylindrical shapehaving a height of about 2˜6 mm and has pores that communicate in agas-communicating direction, is sintered and bonded with the leading endof the vertical holes 105. The porous ceramic sintered body 114 isformed of an alumina-based material. A gas-communicating path formed bythe communicated pores has a narrow pore diameter of equal to or lessthan 10 μm, a dielectric loss in the range of 5×10⁻³ and 1×10⁻⁵, anaverage crystal diameter of equal to or less than 10 μm, a porositybetween 20˜75%, an average pore diameter of equal to or less than 10 μm,a maximum porosity equal to or less than 75 μm, and a bending strengthbeing equal to or more than 30 MPa.

Examples of manufacturing the shower plate 106 sintered and bonded withthe porous ceramic sintered body 114 will now be described below.

(Manufacturing Example 1)

A green body for a shower plate, which is molded according topredetermined dimensions of outer diameter, thickness, horizontal holes,and vertical holes, is prepared after press-molding sprayed granulatedpowder having an average particle diameter of 70 μm, which is obtainedby mixing Al₂O₃ powder having an average powder particle diameter of 0.6μm and a purity of 99.99% with 3 mass % wax at various pressures of78˜147 MPa.

Meanwhile, with regard to a porous ceramic sintered body, a green bodyis obtained by adding the 3 mass % wax to the Al₂O₃ powder for theshower plate and press-molding the mixture of the Al₂O₃ powder with the3 mass % wax after obtaining pre-sintered powder by baking the sprayedgranulated powder at 800° C. A powder molding body obtained byprocessing the green body in a predetermined shape, a debinded bodyobtained by sintering the powder molding body at 450° C., a pre-sinteredbody obtained by sintering the powder molding body at 1000° C., and asintered body obtained by sintering the powder molding body at 1450° C.are prepared.

Also, the green body for the shower plate has different sinteringcontraction rates due to press-molding pressures. In addition, thesintering contraction rate is 19% at 78 MPa and 16.2% at 147 MPa. Amaterial for the porous ceramic sintered body has different sinteringcontraction rates depending on the porosity or pore diameter and alsodue to press-molding pressures. Thus, the dimension of the porousceramic sintered body is measured after the sintering contraction occursby previously examining the sintering contraction rate whenever theproperties of the porous ceramic sintered body are set.

By calculating the inner diameter of a sintered vertical hole using thesintering contraction rate of the shower plate green body, a powdermolding body, a debinded body, a pre-sintered body, or a sintered bodyof the porous ceramic sintered body having an outer diameter equal toand greater than the inner diameter of the sintered vertical hole by amaximum outer diameter of 50 μm, is fitted into the vertical hole and issimultaneously sintered. Therefore, a strong and secure fit is achieveddue to the sintering coupling force between the vertical hole and thebody fitted into the vertical hole.

A gas-communicating path formed, after the simultaneous sintering isperformed, by pores of the porous ceramic sintered body, incommunication with each other, has a narrow pore diameter of 2 μm, adielectric loss of 2.5×10⁻⁴, an average crystal diameter of 1.5 μm, amaximum crystal diameter of 3 μm, a porosity of 40%, an average porediameter of 3 μm, a maximum pore diameter of 5 μm, and a bending degreeof 300 MPa.

(Manufacturing Example 2)

A debinded body is obtained by baking the same green body for the showerplate as described in the manufacturing example 1, at 450° C. Thesintering contraction rate of the debinded body is the same as that ofthe green body.

A pre-sintered body is obtained by baking (pre-sintering) the green bodyfor the shower plate at 600° C.˜1000° C. Since a slight sinteringcontraction occurs in the pre-sintering operation, the higher thepre-sintering temperature is, the less the sintering contraction rate ofthe remains when the pre-sintered body is sintered.

Meanwhile, since the porous ceramic pre-sintering body material obtainedby using the same method as described in the manufacturing example 1uses powder particles obtained by pre-sintering the sprayed granulatedpowder and the porous ceramic pre-sintering body material has asintering contraction rate slightly less than the green body for theshower plate, the outer diameter dimension of the vertical hole of thegreen body for the shower plate can be designed by measuring the outerdiameter dimension with regard to the same temperature as the sinteringtemperature of the shower plate or by calculating the outer diameterdimension using the contraction rate of the shower plate.

In the same manner as described in the manufacturing example 1, a showerplate material and the porous ceramic sintering body material fittedinto the vertical hole are simultaneously sintered, thereby producingthe sintering coupling force between the shower plate and the porousceramic sintered body, so that a strong and secure fit is achieved.

In this regard, the thickness d of a plasma sheath thickness formed onthe surface of an object contacting plasma is expressed according toequation 1 below,

$\begin{matrix}{d = {0.606{\lambda_{D}\left( \frac{2\; V_{0}}{T_{e}} \right)}^{3/4}}} & \left. 1 \right)\end{matrix}$

wherein V₀ denotes an electric potential difference (in units of V)between the plasma and the object, Te denotes an electron temperature(in units of eV), and λ_(D) denotes a Debye length expressed accordingto equation 2 below,

$\begin{matrix}\begin{matrix}{\lambda_{D} = \sqrt{\frac{ɛ_{0}{kT}_{e}}{n_{e}e^{2}}}} \\{= {7.43 \times 10^{3}{\sqrt{\frac{T_{e}\left\lbrack {e\; V} \right\rbrack}{n_{e}\left\lbrack m^{- 3} \right\rbrack}}\lbrack m\rbrack}}}\end{matrix} & \left. 2 \right)\end{matrix}$

wherein ∈₀ denotes vacuum magnetic permeability, k denotes a Boltzmannconstant, and n_(e) denotes electron density of plasma.

Referring to Table 1, as the electron density of plasma increases andthe Debye length becomes small, a hole diameter of the porous ceramicsintered body 114 may be preferably smaller, so as to prevent thereverse flow of the plasma. In more detail, the size of the average porediameter may be equal to or less than twice the thickness of the plasmasheath, and preferably equal to or less than the thickness of the plasmasheath. A pore of the porous ceramic sintered body 114 of the presentinvention, i.e. a narrow path along which gas can communicate, is equalto or less than 10 μm, which is the same as the thickness of a sheath ofhigh-density plasma of 10¹³ cm⁻³. Therefore, the shower plate can beused for the high-density plasma of 10¹³ cm⁻³.

TABLE 1 T_(e) = 2 eV, V₀ = 12 V Plasma Density Debye Length SheathThickness (cm⁻³) (mm) (mm) 10¹³ 0.003 0.01 10¹² 0.011 0.04 10¹¹ 0.0330.13 10¹⁰ 0.105 0.41

Next, a method of introducing plasma excitation gas into a processingchamber will now be described with reference to FIG. 1. The plasmaexcitation gas is introduced via the gas inlet port 110, into thevertical holes 105 via the gas supply hole 111 and the spaces 112, andis exhausted from the porous ceramic sintered body 114 sintered andbonded with the leading end of the vertical holes 105 to the processingchamber 102.

A slot plate 116 of a radial line slot antenna in which a plurality ofslits are opened to irradiate microwaves, a wavelength shortening plate117 for propagating microwaves in a diameter direction, and a coaxialwaveguide plate 118 for introducing microwaves into the radial line slotantenna are disposed on the upper surface of the cover plate 108covering the upper surface of the shower plate 106. The wavelengthshortening plate 117 is inserted between the slot plate 116 and a metalplate 119. A cooling flow path 120 is formed in the metal plate 119.

In the above construction, the plasma excitation gas supplied from theshower plate 106 is ionized by microwaves irradiated from the slot plate116, so that high-density plasma is generated in a region of several mmdirectly below the shower plate 106. The high-density plasma spreads andreaches the substrate 103 to be processed. In addition to the plasmaexcitation gas, oxygen gas or ammonia gas may be introduced from theshower plate 106 as gas for actively generating radicals.

A lower shower plate 121 formed of a conductor, such as aluminum orstainless steel, is disposed between the shower plate 106 and thesubstrate 103 to be processed in the processing chamber 102 of theplasma processing apparatus. The lower shower plate 121 includes aplurality of gas-communicating paths 121 a for introducing process gassupplied via a process gas supply port 122 to the substrate 103 to beprocessed in the processing chamber 102. The process gas is exhausted tothe space between the lower shower plate 121 and the substrate 103 to beprocessed, through a plurality of nozzles 121 b formed in a surface ofthe gas-communicating paths 121 a corresponding to the substrate 103 tobe processed. With regard to a plasma-enhanced chemical vapor deposition(PECVD) process, when a silicon thin film is formed, silane gas ordisilane gas is introduced as the process gas, and when a low dielectricfilm is formed, C₅F₈ gas is introduced as the process gas. A CVD processusing organic metal gas as the process gas is possible. With regard to areactive ion etching (RIE) process, C₅F₈ gas or the oxygen gas isintroduced as the process gas for silicone oxide film etching, andchlorine gas or HBr gas is introduced as the process gas for metal filmor silicone etching. When etching requires ion energy, RF power isapplied by connecting an RF power source 123 to an electrode installedin the holding stage 104 through a capacitor, thereby generating a selfbias voltage onto the substrate 103 to be processed. The type of processgas to be supplied is not limited thereto, and the process gas to besupplied and its pressure are set depending on a process.

A plurality of openings 121 c are formed between the adjacentgas-communicating paths 121 a of the lower shower plate 121 so thatplasma excited by microwaves in the upper part of the lower shower plate121 diffuses to pass through into spaces between the substrate 103 to beprocessed and the lower shower plate 121 in an efficient manner.

Heat flows that flow into the shower plate 106 due to exposure to thehigh density plasma are exhausted by a refrigerant such as water flowingalong the cooling flow path 120 via the slot plate 116, the wavelengthshortening plate 117, and the metal plate 119.

The shower plate 106 is used for the plasma processing apparatus havingthe above construction, so that the porous ceramic sintered body 114sintered and bonded with the vertical hole 105 does not become detachedfrom the vertical hole while the shower plate 106 is being used, and thereverse flow of plasma to a gas inlet side can be more completelyprevented. Thus, an abnormal discharge or deposition of plasma in theshower plate 106 is prevented, thereby preventing deterioration oftransmission efficiency of microwaves for exciting plasma ordeterioration of yield.

As a result of uniformly supplying the plasma excitation gas to thesubstrate 103 to be processed and supplying the process gas through thenozzles 121 b from the lower shower plate 121 to the substrate 103 to beprocessed, the process gas uniformly flows from the nozzles 121 b formedin the lower shower plate 121 to the substrate 103 to be processed, sothat a component of the process gas which returns to the upper part ofthe shower plate 106 is reduced. As a result, decomposition of processgas molecules according to an excessive dissociation due to exposure tothe high density plasma is reduced, and even if the process gas isdeposition gas, deterioration of microwaves transmitting efficiencycaused by the deposition of the process gas to the shower plate 106 isdifficult to occur, which reduces a cleaning time and increases processstability and reproducibility, thereby increasing productivity andrealizing high quality substrate processing.

FIGS. 4( a) through 4(c) are views of another structure of the verticalhole 105. FIG. 4( a) is a cross-sectional view of the vertical hole 105.FIGS. 4( b) and 4(c) are bottom plan views of the vertical hole 105. Aceramic member 113 is sintered and bonded with the vertical hole 105.The ceramic member 113 is formed of alumina ceramic and has an outerdiameter of 3.0 mm and a full length of 8 mm. A plurality of gas releaseholes 113 a each having a diameter of 0.05 mm and a length of 8 mm areformed in the ceramic member 113. That is, an aspect ratio (length/holediameter) of each gas release hole 113 a is 8/0.05=160. The number ofthe gas release holes 113 a is not particularly limited. Although 7 gasrelease holes 113 a and 3 gas release holes 113 a are respectively shownin FIGS. 4( b) and 4(c), a gas release speed may be reduced by possiblyusing a larger number of gas release holes 113 a. When the diameter ofthe gas release holes 113 a is reduced to 0.05 mm, the outer diameter ofthe ceramic member 113 may be reduced to about 1 mm.

Also, the length of the gas release holes 113 a may be longer than themean free path of electrons, that is, the average distance electronstravel without collision. Table 2 shows the mean free path of electrons.The mean free path is in adverse proportional to a pressure, and is 4 mmat the pressure of 0.1 Torr. Since the gas inlet side of the gas releaseholes 113 a is actually under high pressure, Since the mean free path isshorter than 4 mm due to high pressure in the gas inlet side of the gasrelease holes 113 a, the length of the gas release holes 113 a of thepresent invention is 8 mm, which is longer than the mean free path.

TABLE 2 Mean free path of electrons in the atmosphere of Ar gas Pressure(P) Mean Free Path (λen) (Torr) (mm) 10 0.04 1 0.4 0.1 4 λen (mm) =0.4/P (Torr)

Also, with regard to the vertical hole 105 shown in FIGS. 4( a) through4(c), chamfer processing 115 is performed on a corner portion of the gasinlet side of the vertical hole 105 in order to prevent self-generationof plasma by igniting the plasma excitation gas due to a concentratedmicrowave electric field. The chamfer processing 115 may be C chamferprocessing, preferably R chamfer processing. R chamfer processing may beperformed after the C chamfer processing is performed in order toachieve the chamfer processing 115.

Referring to FIGS. 4( a) through 4(c), the shower plate 106 sintered andbonded with the ceramic member 113 can be manufactured by using the samemethods as described in the manufacturing examples 1 and 2. Anothermanufacturing example is described below.

(Manufacturing Example 3) With respect to a ceramic member, a mixingbody, obtained by adding a cellulose injection molding binder of 4% andan adequate amount of water to Al₂O₃ powder having an average powderparticle diameter of 0.6 μm and a purity of 99.99%, is prepared, and aninjection molding body is obtained from an injection metal mold in which24 pins of 80 μm are installed in mold nozzle having an inner diameterof 16 mm.

After drying the injection molding body, the dried body and a debindedbody which is processed at a temperature of 450° C. are sintered at atemperature of 150° C. As a result, the dried body and the debinded bodyform a ceramic member having an outer diameter of 1.0 mm and includinggas release holes each having a hole diameter of 50 μm, thus, thecontraction rate from the mold dimensions is proved to be 37.5%.

Meanwhile, the exact same green body for the shower plate as describedin the manufacturing example 1 is prepared, except that a moldingpressure of sprayed granulated powder is set to be 147 MPa, and threetypes of molding bodies including the vertical holes respectively havinginner diameters of 1.16 mm, 1.135 mm, and 1.19 mm are manufactured.

Since the sintering contraction rate of the green body for the showerplate is 16.2%, the molding bodies include the vertical holes havinginner diameters of 0.972 mm, 0.951 mm, and 0.997 mm, respectively. Theceramic member having the outer diameter of 1.0 mm and including the gasrelease holes each having the hole diameter of 50 μm is fitted into thevertical holes of the green body for the shower plate and issimultaneously sintered, so that a stress of tightening the ceramicmember with the inner diameters of the vertical holes cause differencesof 0.028 mm, 0.049 mm, and 0.003 mm, respectively, between the diameterdimensions.

The differences between the diameter dimensions caused by the tighteningstress are 0.049 mm (about 50 μm), 0.028 mm (about 30 μm), and 0.003 mm(3 μm). When the differences between the diameter dimensions are about50 μm and 30 μm, it might be expected that the ceramic member iscompressed and thus destroyed or the vertical holes are pressed and thuscracks occur in the vertical holes. However, the ceramic member is notdestroyed or cracks do not occur in the vertical holes and thedifferences between the diameter dimensions are estimated to have beenabsorbed by a slight thermal plasticity therebetween at a hightemperature during the simultaneous sintering and by a slidingphenomenon of crystalline grain boundaries.

Also, since surfaces joined between the inner surface of the verticalholes and the outer surface of the ceramic member are sintered andintegrally bonded, although a gap of about 2 μm partially exists, theshower plate having a uniform crystal structure in which gaps may act ascommunication paths for the plasma excitation gas do not exist, andcrystalline particles continuously exist over a joining boundary withoutforming the joining boundary.

(Manufacturing Example 4)

Instead of the ceramic member sintered at 1500° C., a ceramic memberpre-sintered at 1100° C. is used. The pre-sintered ceramic member isfitted into a green body for a shower plate that is molded to have anouter diameter of 1.15 mm and a vertical hole having an inner diameterof 1.19 mm, and is simultaneously sintered. The present manufacturingexample 4 has the same effect as the manufacturing example 3.

(Manufacturing Example 5)

The injection molding body of the ceramic member used in themanufacturing example 3 has a large sintering contraction rate, and thusthe outer diameter dimension of the injection molding body is greaterthan the inner diameter dimension of the vertical holes that are moldedin the green body for the shower plate. Thus, the injection molding bodycannot be fitted into the vertical hole.

However, if 2% of the injection molding binder used in the manufacturingexample 3 is mixed with 0.5% of a deflocculant, it is possible to reducea moisture content of a mixing body. Also, although the sinteringcontraction rate of the ceramic member manufactured at a plungerinjection molding pressure of 1.5 ton/cm² is 28% with regard to the molddimension, a dried body having an outer diameter dimension of 1.15 mm isobtained by contracting the metal molding dimension by 10% when dryingthe injection molding body. In more detail, the sintering contractionrate of the dried body is 18%, less than the sintering contraction rateof 19% of the green body for the shower plate molded, which is achievedby using 78 MPa in the manufacturing example 1. Thus, although it ispossible and natural to fit the ceramic member into the vertical hole ofthe green body for the shower plate and simultaneously sinter theceramic member fitted into the vertical hole in the step of theinjection molding body (powder molding body) before being baked, it isalso possible to fit a debinded body of the injection molding body(powder molding body), a pre-sintered body thereof, and a sintered bodythereof into the vertical holes of the green body for the shower plateand simultaneously sinter the bodies fitted into the vertical holes.

In more detail, as described above, by measuring the sinteringcontraction rates of various molding pressures of the shower plate andthe sintering contraction rates of various mixing bodies of the ceramicmember or at every molding pressure, it is possible to fit the injectionmolding body (powder molding body) of the ceramic member, a debindedbody of the injection molding body, a pre-sintered body of the injectionmolding body, or a sintered body of the injection molding body into thevertical hole of the green body of the shower plate, a debinded body ofthe green body, or a pre-sintered body of the green body, andsimultaneously sinter the body fitted into the vertical hole, therebyobtaining the shower plate, having no gap, that is sintered and bondedintegrally with the ceramic member and the vertical hole of the showerplate.

An integral sintered body without a gap is also obtained by fitting theceramic member sintered at a high temperature of 1500° C. into thevertical hole of the shower plate pre-sintered to have a relativedensity of 96% and simultaneously sintering the ceramic body fitted intothe vertical hole in a HIP processing device at a temperature of 1400°C. and a pressure of 1500 kg/cm².

Although the high purity alumina ceramic material is used in themanufacturing examples 1 through 5, if a low dielectric loss ceramicmaterial has a dielectric loss in the range of 5×10⁻³ and 1×10⁻⁵, asmall amount of a grain growth inhibition agent, an alumina ceramicmaterial mixed with Y₂O₃ and mullite, a material formed of Al₂O₃ andY₂O₃, or a material containing a garnet component that is a compound ofAl₂O₃ and Y₂O₃, and further a ceramic material such as AlN, SiO₂,mullite, Si₃N₄, or SiAlON, can be used.

A combination of the ceramic material for the shower plate and theceramic material for gas release hole members (the porous ceramicsintered body and ceramic member) is not particularly limited but thematerial component of the ceramic materials may be the same.

In addition, when the gas release hole members are fitted (inserted)into vertical holes and are integrally sintered, it is possible toattain the same function and effect as an adhesive agent by coating theouter surface of the gas release hole members with fine powder of samematerial component, thereby obtaining the same result as obtained in theprevious manufacturing examples.

FIGS. 5( a) and 5(b) are views of another structure of the vertical hole105.

Referring to FIG. 5( a), as a double security measure for preventing thereverse flow of plasma, the ceramic member 113 is additionally disposedin the gas inlet side of the porous gas ceramic sintered body 114, andthe ceramic member 113 and the porous gas ceramic sintered body 114 aresintered and bonded with the vertical hole 105 of the shower plate 106.Referring to FIG. 5( b), a porous ceramic sintered body 114 a isadditionally disposed in the gas inlet side of the porous gas ceramicsintering body 114, and the porous ceramic sintered body 114 a and theporous gas ceramic sintered body 114 are sintered and bonded with thevertical hole 105 of the shower plate 106. In this case, in order toreduce a pressure loss of plasma excitation gas, the porous ceramicsintered body 114 a disposed in the gas inlet side has greater porosityand a greater pore diameter than the porous gas ceramic sintered body114 on a gas release side (for example, average pore diameter: 10˜30 μm,porosity: 50˜70%).

The number, diameter, and length of the vertical holes 105, and thenumber, diameter, and length of gas release holes 113 a in the ceramicmember 113 are not limited to the numerical values described in thepresent embodiment.

Embodiment 2

FIG. 6 is a cross-sectional view of a microwave plasma processingapparatus according to another embodiment of the present invention. Likereference numerals in the previous embodiment with reference to FIGS. 1through 5 denote like elements.

In the present embodiment, a shower plate 200 is attached to an upperportion of the processing chamber 102 through the sealing O-ring 107 ata position corresponding to the substrate 103 to be processed on theholding stage 104, as a part of the outer walls of the processingchamber 102. The shower plate 200 is formed of dielectric alumina havinga relative permittivity of 9.8, and a low microwave dielectric loss(equal to or less than 9×10⁻⁴). Also, two sealing O-rings 202 and aring-shaped space 203 surrounded by the side surface of the shower plate200 are formed at a position corresponding to the side surface of theshower plate 200 on a wall surface 201 of the processing chamber 102.The ring shaped space 203 communicates with the gas inlet port 110 forintroducing plasma excitation gas.

Meanwhile, a plurality of horizontal holes 204 each having a diameter of1 mm in a horizontal direction are formed in the side surface of theshower plate 200 and are opened in a center direction of the showerplate 200. At the same time, a plurality (230) of vertical holes 205communicate with the processing chamber 102 so as to communicate withthe horizontal holes 204.

FIG. 7 is a top plan view of the arrangement of the horizontal holes 204and the vertical holes 205 of the shower plate 200. FIG. 8 is aschematic perspective view of the arrangement of the horizontal holes204 and the vertical holes 205 of the shower plate 200.

The shower plate 200 of the present embodiment can be formed bysintering and bonding a ceramic member or a porous gas-communicatingbody into the vertical holes 205 in the same manner as described in theprevious embodiment.

INDUSTRIAL APPLICABILITY

The shower plate of the present invention can be used for various plasmaprocessing apparatuses, such as parallel-plate type high frequencyexcitation plasma processing apparatuses, induction-coupled type plasmaprocessing apparatuses, in addition to a microwave plasma processingapparatus.

What is claimed is:
 1. A method of manufacturing a shower plate which isto be disposed in a plasma processing and to discharge a plasmaexcitation gas so as to generate plasma in the plasma processingapparatus, the method comprising: providing a first ceramic memberhaving a plurality of vertical holes, wherein the plurality of verticalholes are to be release paths for the plasma excitation gas; fittingeach of a plurality of second ceramic members into each of the verticalholes, wherein each of the second ceramic members has a plurality of gasrelease holes; and sintering the first ceramic member and the secondceramic members fitted into the vertical holes of the first ceramicmember.
 2. The method of claim 1, wherein the first ceramic member is agreen body formed by molding material powder of a shower plate and byprocessing the vertical holes, a debinded body of the green body, or apre-sintered body of the green body, and the each of the second ceramicmembers is: a powder molding body processed in a predetermined shape bymolding material powder of a shower plate, a debinded body of the powdermolding body, a pre-sintered body of the powder molding body or asintered body of the powder molding body, and/or a powder molding bodyprocessed in a predetermined shape by molding material powder of aporous gas-communicating body, a debinded body of the powder moldingbody, a pre-sintered body of the powder molding body or a sintered bodyof the powder molding body.
 3. The method of claim 1, wherein an aspectratio of length to hole diameter of each of the gas release holes isequal to or greater than
 20. 4. The method of claim 2, wherein an aspectratio of length to hole diameter of each of the gas release holes isequal to or greater than
 20. 5. The method of claim 1, wherein each ofthe gas release holes has a diameter of 20 μm to 70 μm.
 6. The method ofclaim 2, wherein each of the gas release holes has a diameter of 20 μmto 70 μm.
 7. The method of claim 3, wherein each of the gas releaseholes has a diameter of 20 μm to 70 μm.
 8. The method of claim 4,wherein each of the gas release holes has a diameter of 20 μm to 70 μm.